If I take a typical mini system with one speaker wired next to it and the other speaker wired 100m away will it work? is there a minimum wire size i should get, looking for the cheapest wire aswell. Could i use standard wire or does it have to be speaker wire?

Depends on the resistance of the wire. A friend and I used to get stuff from a dollar store type supplier. They had speaker wire. The resistance was about 30 ohms over the 100m roll, so it would really stuff up the levels of a typical 4 ohm speaker.

When running over long distances for PA type use, they use 70 or 100 volt systems, which have a transformer at the speaker to make it appear as a much higher impedance, so the wire is less important for loss. But that needs an amp with the right output and a transformer that you set the power levels on, probably more hassle than a second mini system and some other way to get the audio there wirelessly.

100 metres? Seriously? What are you trying to do with that kind of separation? If you really want to do that, I would suggest that you probably want the heaviest gauge wire you can manage. Maybe you should also connect both speakers with the same length of that wire regardless of their position to balance things out a little. There are experts here who can tell you a lot more than I can.

I work in a large open building with a radio at one end which is too far away to hear reasonably if you are at the main end, hence wanting to have a speaker at each end. Cannot place speaker in middle.

Could put radio in middle with speakers wired 50m away on each side. Wifi is throughout the building and could also be an option. Looking for the cheapest solution.

mb82: I work in a large open building with a radio at one end which is too far away to hear reasonably if you are at the main end, hence wanting to have a speaker at each end. Cannot place speaker in middle.

Could put radio in middle with speakers wired 50m away on each side. Wifi is throughout the building and could also be an option. Looking for the cheapest solution.

Is there a mains socket at the far end? If so, why not just put another cheap radio at the other end?

mb82: I work in a large open building with a radio at one end which is too far away to hear reasonably if you are at the main end, hence wanting to have a speaker at each end. Cannot place speaker in middle.

Could put radio in middle with speakers wired 50m away on each side. Wifi is throughout the building and could also be an option. Looking for the cheapest solution.

Is there a mains socket at the far end? If so, why not just put another cheap radio at the other end?

That was my thought - just have another cheap radio at the far end. You could probably pick up a second radio cheaper than 100m of speaker cable of the gauge you'd need to get even half-way decent sound.

Why can't you put a speaker in the middle? Could you put the whole system in the middle?

Can't have speaker in the middle as it is too close to office. By radio I mean radio / aux input. Did have cheap radio at other end but were only allowed 1 on at a time, think they ran out of sync if I remember correctly

They won't be out of sync, it's just the 1/3 second or so delay for sound to travel 100m in air. Running a speaker on the end of 100m of cable will still have the same problem. Either turn the volume up, and have one sound source, or have two sound sources low enough that you don't hear the furtherest one.